Function calculate_intersection_point_distances 

pub fn calculate_intersection_point_distances(
    a1: &Vector3d,
    pole1: &Vector3d,
    length1: Radians,
    a2: &Vector3d,
    pole2: &Vector3d,
    length2: Radians,
    centroid: &Vector3d,
) -> (Radians, Radians)

Calculate the great-circle distances along a pair of arcs to their closest intersection point or their coincident arc distances if the Arcs are on coincident Great Circles.

• a1, a2 the Arc start points.
• pole1, pole1 the Arc poles.
• length1, length2 the Arc lengths.
• centroid the centroid (geometric mean) of the Arcs mid points.

returns the distances along the first arc and second arc to the intersection point or to their coincident arc distances if the arcs do not intersect.